Despite all that Trump enthusiasm, Icahn's hedge fund seems to be positioning for the end of the Trump party.

Icahn Enterprises(IEP), which Icahn controls and serves as chairman of, quietly disclosed last week that it had a net short position in its investment portfolio of 128% as of the end of last year. That's a fivefold increase from the end of 2015.

The net short position means Icahn's firm is betting against 1.3 shares for every one share it's betting on. In other words, Icahn's investment portfolio will generally gain value when prices decline, and vice versa.

"I am concerned at this point that the market has run ahead of itself," Icahn told CNNMoney in a phone interview on Tuesday.

Icahn said one "worrisome thing is that so much money has run into ETFs." Icahn voiced concern that the flood of retail money into passive investments like ETFs will create a stampede when markets turn south.

However, Icahn explained that his firm isn't as negative as suggested by the net short figure, which only covers its investment segment and not its various other holdings.

He noted that Icahn Enterprises has a lot of control positions that are not counted in the investment segment. For instance, Icahn Enterprises owns Pep Boys and manufacturer Federal-Mogul.

But Icahn Enterprises' top executives sounded very cautious during last week's conference call.

"We continue to have a fairly bearish view," Icahn Enterprises CEO Keith Cozza said during the call.

"The market does seem to be priced for perfection," he said.

Besides the short position, Icahn's firm is also taking some defensive maneuvers. In December, it sold American Railcar Leasing for up to $3.4 billion and last week it unloaded the shuttered Trump Taj Mahal casino in Atlantic City to the company behind the Hard Rock Café for an undisclosed sum.

The investment company also refinanced $1.2 billion of debt and raised $600 million in cash through a stock offering. The firm's balance sheet has slashed its total debt to the lowest level in nearly three years.

"It's not the greatest time for large, long investments," Icahn's CEO said during the call.

Icahn executives voiced concern about "very high market multiples."

The S&P 500 is trading at 17.9 times forward earnings, the highest P/E ratio since 2004, according to FactSet.

Valuation levels have climbed to high levels because the big Trump rally -- the S&P 500 is up 11% since November 8 -- has been fueled by expectations of tax cuts and other stimulus, not fundamental improvement in corporate profits.

Icahn's cautious positioning stands in contrast to his opportunistic stance back in early November. As global markets panicked over Trump's victory, Icahn literally left the victory party in Manhattan early to buy "a lot of stock" in overnight markets.